B757-200 Flight Attendant reported that maintenance had to arm aircraft door and verify visually that escape slide was engaged due to slide indication light being inoperative.

Narrative

Maintenance had to arm my door during boarding due to slide indication light being inoperative. He had to lay in the floor to verify the slide was engaged. I was instructed not to touch this door until arrival at ZZZ. At that time I disarmed this door as normal. I also wrote a report in an effort to avoid an inadvertent slide deployment. Please note this is a 757-200.Addtl info from FA B: Also called cabin crew at ZZZ1 and entered this information on the app. Additional comment. The maintenance technician and I were at door 4L before catering arrived for that flight. The technician proceeded to arm that door without placing the red streamer across the viewing window. I told him stop!" And corrected him. I then had to remind him catering had not arrived and would be opening that door and it needed to be disarmed. I worry that if I wasn't present; there was a high possibility of an inadvertent slide deployment. Important: I have referenced my manual and read the 757-200 door slide will not deploy if opened from the outside."